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Robert Levinson's family: We won't stop until you're home

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Dan Levinson said the family realizes time is of the essence

Levinson was not among five American hostages that Iran released in January

New York (CNN)Two children of the longest-held hostage in American history are hoping a series of meetings this week in Washington will renew efforts to find their father nearly 10 years after he disappeared in Iran.

The family of Robert Levinson, a retired FBI agent -- and, according to his family, a CIA contractor -- met with Secretary of State John Kerry, members of Congress and top aides to President Barack Obama at the White House, including National Security Adviser Susan Rice.

In an exclusive interview with CNN's Erin Burnett on "Outfront," Dan Levinson said White House officials "told us that they are working on the case, and they are not going to rest until he is home safe to us."

Levinson said the family realizes time is of the essence since there will be a new administration in January.

"We are hoping with this limited time window and with Iranian elections coming up that the urgency is now more than ever and that they are doing everything they can to bring him home," he said.

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Levinson was not among five American hostages that Iran released in January. The Obama administration said $400 million that was part of $1.7 billion owed to Iran was withheld until the hostages were released, but has insisted it was not a ransom payment.

Sarah Moriarty, Levinson's daughter, said that left the family "absolutely devastated" and it was difficult to accept since "it's been nine and a half years that he has been without basic human rights."

The payment to Iran also upset Dan Levinson.

"There was a lot of leverage and avenues that they could engage with the Iranians," he said. "That was a lot of money and obviously we would have liked to see if there was any kind of connection with that and then that should have been more than enough to bring my dad home."

The Levinson family says it fully believes that Robert Levinson is alive, and that all indications from the FBI and investigators support that.

Asked if she had a message for her father, Moriarity said, "It's always we love you. We will never stop until you come home. You have so many people here fighting every single day to bring you home, and we love you very much, and you have several grandchildren that can't wait to meet their Grandpa Bob."

FBI investigators believe Robert Levinson, if he is still alive, is being held in Iran, US officials briefed on the investigation told CNN in January.

Levinson vanished after traveling to the Iranian island of Kish in March 2007. His family has said he was looking into cigarette smuggling, and the FBI has said he was working on behalf of several large corporations. An email obtained by the family indicated he was trying to investigate corruption involving Iranian officials.

But he was also doing independent contract work for the CIA at the time, the Levinson family eventually confirmed.

The CIA has not confirmed that allegation. But three CIA employees -- including Levinson's handler -- were eventually fired, and seven others disciplined in connection with the case, and the CIA paid the family $2.5 million to avoid a lawsuit, a family attorney has told CNN.